This proposal requests support for the Sixth International Conference on Legionella to be held October 16-20, 2005 at the Hyatt Regency in Chicago, IL. Based on attendance at prior meetings, the meeting location, and the fact that major recent advances have been made on Legionella, ca. 400 registrants are expected. Attendees will be doctoral level scientists, physicians, public health officials, environmental engineers, medical and graduate students, and post-doctoral level trainees in the basic sciences and clinical medicine. Attendees are expected from more than 25 different countries. The scientific program will address five major topics; clinical aspects of the disease, public health issues, bacterial pathogenesis and host immunity, and environmental aspects including disease prevention. The clinical aspects topics will include keynote lectures on the clinical diagnosis, treatment, and laboratory diagnosis of Legionnaires' Disease. Public health lectures will address the investigation of sporadic and epidemic Legionnaires' Disease, risk factors for the disease, and public health measures for disease prevention. Experts in microbiology, cell biology, and immunology will address the amazing recent advances in understanding how the bacterium subverts host defenses to cause disease, as well as how knowledge about the interaction of the bacterium with the host advances knowledge in cell biology and the human immune response to intracellular pathogens. Environmental microbiologists and engineers will discuss the environmental ecology of the bacterium, the best methods to detect the organism in the environment, and how best to design buildings to prevent the disease from occurring. Thus, attendees will obtain the latest information on all aspects related to Legionella and Legionnaires' Disease and have the opportunity to initiate and/or strenghten collaborations with scientists throughout the world. This unique gathering of microbiologists, physicians, public health officials, and engineers is the definitive meeting for those concerned with Legionella and its associated diseases.